Creating Custom Transport Layer

Wails v3 allows you to provide a custom IPC transport layer while retaining all generated bindings and event communication. This enables you to replace the default HTTP fetch-based transport with WebSockets, custom protocols, or any other transport mechanism.

Overview

By default, Wails uses HTTP fetch requests from the frontend to communicate with the backend via /wails/runtime. The custom transport API allows you to:

Replace the HTTP transport with WebSockets, gRPC, or any custom protocol
Maintain full compatibility with Wails code generation
Keep all existing bindings, events, dialogs, and other Wails features
Implement your own connection management, authentication, and error handling

Architecture

┌─────────────────────────────────────────────────┐
│  Frontend (TypeScript)                          │
│  - Generated bindings still work                │
│  - Your custom client transport                 │
└──────────────────┬──────────────────────────────┘
                   │
                   │ Your Protocol (WebSocket/etc)
                   │
┌──────────────────▼──────────────────────────────┐
│  Backend (Go)                                   │
│  - Your Transport implementation                │
│  - Wails MessageProcessor                       │
│  - All existing Wails infrastructure            │
└─────────────────────────────────────────────────┘

Usage

1. Implement the Transport Interface

Create a custom transport by implementing the Transport interface:

package main

import (
    "context"
    "github.com/wailsapp/wails/v3/pkg/application"
)

type MyCustomTransport struct {
    // Your fields
}

func (t *MyCustomTransport) Start(ctx context.Context, processor *application.MessageProcessor) error {
    // Initialize your transport (WebSocket server, gRPC server, etc.)
    // When you receive requests, call processor.HandleRuntimeCallWithIDs()
    return nil
}

func (t *MyCustomTransport) Stop() error {
    // Clean up your transport
    return nil
}

2. Configure Your Application

Pass your custom transport to the application options:

func main() {
    app := application.New(application.Options{
        Name: "My App",
        Transport: &MyCustomTransport{},
        // ... other options
    })

    err := app.Run()
    if err != nil {
        log.Fatal(err)
    }
}

3. Modify Frontend Runtime

If using a custom transport, you’ll need to modify the frontend runtime to use your transport instead of HTTP fetch. Implement RuntimeTransport interface that will be used to handle requests:

const { setTransport } = await import('/wails/runtime.js');

class MyRuntimeTransport {
  call(objectID: number, method: number, windowName: string, args: any): Promise<any> {
    // TODO: implement IPC call with your transport protocol

    return resp;
  }
}

const myTransport = new MyRuntimeTransport();
setTransport(myTransport);

Notes

The default HTTP transport continues to work if no custom transport is specified
Generated bindings remain unchanged - only the transport layer changes
Events, dialogs, clipboard, and all other Wails features work transparently
You’re responsible for error handling, reconnection logic, and security in your custom transport
The WebSocket example provided is for demonstration and may need hardening for production use

API Reference

Transport Interface

type Transport interface {
    Start(ctx context.Context, messageProcessor *application.MessageProcessor) error
    // JSClient returns the JavaScript shim that the runtime injects into the
    // window so that frontend code can call into the transport.
    JSClient() []byte
    Stop() error
}

AssetServerTransport Interface (Optional)

For browser-based deployments or when you want to serve both assets and IPC through your custom transport, implement the AssetServerTransport interface:

type AssetServerTransport interface {
    Transport

    // ServeAssets configures the transport to serve assets alongside IPC.
    // The assetHandler is Wails' internal asset server that handles all assets,
    // runtime.js, capabilities, flags, etc.
    ServeAssets(assetHandler http.Handler) error
}

When to implement this interface:

Running the app in a browser instead of a webview
Serving assets over HTTP alongside your custom IPC transport
Building network-accessible applications

Example implementation:

func (t *MyTransport) ServeAssets(assetHandler http.Handler) error {
    mux := http.NewServeMux()

    // Mount your IPC endpoint
    mux.HandleFunc("/my/ipc/endpoint", t.handleIPC)

    // Mount Wails asset server for everything else
    mux.Handle("/", assetHandler)

    // Start HTTP server
    t.httpServer.Handler = mux
    go t.httpServer.ListenAndServe()

    return nil
}

When ServeAssets() is called, the assetHandler provides:

All static assets (HTML, CSS, JS, images, etc.)
/wails/runtime.js - The Wails runtime library